Nitrogen Cycle and Moving Bed Filter

Nitrogen Cycle

Nitrogen Cycle

One of the most important concepts in aquaponics is the nitrogen cycle. Without a full understanding of it, you will not know "how" aquaponics actually works. But if you take a little bit of time to think about it, its not too hard. 

The fish produce waste, and there is usually some food floating around that does not get eaten. These two when let to sit in an aquarium, start to break up, and this creates ammonia. This is the first step in the nitrogen cycle. While ammonia starts the cycle, it is very dangerous and deadly to fish if the ppm (parts per million) gets too high.

The nitrogen cycle has two naturally occurring bacteria that do most of the work. The first bacteria to aid in the nitrogen cycle is nitrosomonas. This bacteria converts ammonia into nitrites. Fish can tolerate nitrites more than they can ammonia, but it can still be toxic to them. 

Nitrospira is the secnond naturally occurring bacteria that aids the nitrogen cycle. Nitrospira consumes the nitrite produced by nitrosomonas and produces nitrates as a byproduct. Nitrates are much safer for fish than either ammonia or nitrites. However if there is nowhere for the nitrates to go and they are not being consumed, it can kill your fish.

In a home aquarium, the nitrates are removed by doing water changes, or if there are plants in the aquarium, they will consume the nitrates, which is essentially plant food. 

In aquaponics, we not only grow veggies, fruits, and fish, we also cultivate these bacteria. Without nitrosomona and nitrospira, aquaponics would not work the way it does. We use their by-products to feed our plants so we do not need to add fertilizers. 

So the key to aquaponics is producing enough nitrates for your plants to grow, and having enough plants to consume the nitrates. While reading up on different filters for my aquarium (before I converted to aquaponics), I came across moving bed filters. 

Moving Bed Filter

A moving bed filter in short is a nitrate factory. It uses small filter media that have extreme amounts of surface area to catch all the bacteria that flow through the filter. The idea is very similar to the way aquaponics works. The filter media cultivate the same naturally occurring bacteria, nitrosomonas and nirospira. Theses filter the water like a mini nitrogen cycle. The filter media is designed to work best when they are moving around in the water, hence its name. 

Tilapia Approved! 

Moving bed filters use nontraditional filter media. Many products can be used but through my research I found that Hel-X. Hel-x has 40% more surface area than its competitors and comes in an array of sizes.  

Close up of Hel-X filter media.
The surface area on these are impressive!

Usually aquaponic systems do not have filters (well Deep Water Culture does but...), however I believe adding this type of filter would be a huge benefit to aquaponic systems.

When I met Alex Blackwell, I brought with me a bag of Hel-X media. The idea was to build a moving bed filter for his system. After a day or two of collaboration and brainstorming, we got the idea of using a moving bed filter as a prefilter for his pump. 

Alex's pump is in the fish tank and the mechanical filter it came with got clogged weekly with all the fish waste. This slowed the flow rate and turned the water a murky brown color, not the best. We designed and added the moving bed filter to the pump. The pump pulls the water through the moving bed filter and stirs up the Hel-X. It works amazingly!

The filter has cleaned the water and increased the flow rate.
Once the bacteria is fully established, it will provide filtration
and nitrates for the plants.

The moving bed filter in the Blackwell system cleaned up the water and increased flow rate. Once the bacteria has a chance to colonize the Hel-X the filtration will consume the ammonia and decrease ammonia spikes. Plus once it is established, it will be pumping extra nitrates into the grow bed each time the pump runs, which is 15 minutes of each hour.

Raising Baby Tilapia Aquaponicly

Tilapia Fry

The Blackwell System recently had babies (fry)! There have been a few mothers holding eggs, but we never stripped them in time. This time was different, we were ready! 

We were trying an experiment with two mothers at the same time. Alex bought a small terrarium with a screen lid which was submersed into the large aquarium to make a small holding tank. With the two mothers holding eggs, we corralled one of the mothers into the holding tank. Our reasoning; the mother would spit the babies out and then we would release the mother back into the tank and keep the babies in the holding tank. The second mother fish would act as a control, to see how the babies survive (or don't) being spit into the tank directly. 

Things did not go as planned. On the third day, we went to check on the mother in the holding tank first thing in the morning. The mother was in there (where else would she go?), but she was definitely was not holding eggs any more and there was none in the tank. She ate them.

The control mother was still holding her eggs though. We had watched a movie on YouTube about stripping mother tilapia of their eggs the day before, and have decided to try and strip the control mother as we were tired of loosing babies. 

So we set up a bucket we could strip the mother in (that sound dirty!) and caught her in the net. While we where trying to get a good grip on her, she started spitting the eggs out! So we quickly got her in place and got all the eggs out. There were close to forty eggs and newly hatched eggs swimming and sitting in the bowl! It worked! 

We got a turkey baster and transported the eggs and newborns into a plastic vial. We strapped a fiberglass window screen on top so they cannot swim out and placed that under the grow bed drain. And there it hangs!

Water returning from the grow beds flows into the tube and replaces the water.
There are about 30 tilapia fry in the tube.

The fry are growing every day. After the eggs yolk sacks were gone, we have fed them crushed fish food. A good way to tell if fish are healthy is the food test. Fish that eat and have no physical symptoms are usually doing alright.

After they start to crowd this tube, which should not take long, the plan is to move them to the holding tank originally designed to house the holding mothers. The holding tank used to be resting on the bottom of the aquarium but too much fish poop was falling in it. It is now hanging kinda like the hatching tube but is semi-submersed.

Holding tank originally used to house tilapia mothers holding eggs.
When the fry are big enough they will be transferred to this tank.

Being able to strip the mother and raise our own babies has allowed us to close the loop in our system that can now be perpetual and not reliant on buying new tilapia after these ones... Well after these current fish make a tasty meal!

Trouble Shooting pH, Blackwell Aquaponic System

pH

pH is a measure of the activity of the (solvated) hydrogen ion*. To the average aquapon that is very confusing. pH is the way we measure how acidic or alkaline a liquid is. Pure water will have a pH of 7. The pH scale goes from 1-14, 1 being very very acidic and 14 being very very alkaline. Substances with these extreme pH's are extremely dangerous and some can eat through human flesh! Another "cool" property of the pH is its logarithmic. The numbers actually increase and decrees exponentially. 8 is 10x more alkaline that 7, and 9 is 100x more alkaline! The same is true for the acidic side of the scale. So you can see that pH can change FAST and can run wild if left uncorrected.

To figure out what the pH of your aquaponics system should be, you need to take into consideration the organisms living in your system. Plants generally like a pH of 5.0-7.0; Fish like 6.5-8.0; The bacteria and worms (if you do not have worms, I recommend them) like the pH to be 6.0-8.0. This leaves us with some comprising, 6.8-7.0 is supposedly the industry standard. But remember, these are optimal conditions. A system can fluctuate around these numbers and still have a perfectly functioning system. My system at home has a slightly higher pH of 7.5-7.8. My African Cichlids like the water to be a bit harder and to have a tad higher pH. Since I used my existing aquarium for my aquaponics, I did not try and change my pH. 

One reason pH has to be watched in aquaponics is a phenomena called nutrient lockout. When a plant is out of its optimal pH range, it will have trouble up-taking nutrients. This is problematic as you can imagine. If plants are not eating, they will be negatively affected (duh!). Murray Halllam, one of the great aquaponic grandfathers, comments on nutrient lockout and provides a chart in this forum.

My buddy Alex Blackwell has ben having trouble the pH in his system. The Blackwell System has a pH of 8.5! That's quite high! So we are trying to figure it out together. We set up a test to determine what is causing his pH to raise so much. The suspected culprit is the grow stones used in the Blackwell System. 

We wanted to be diligent with our test. Three bowls were gathered. In the first bowl was the top off water. It has a ph of 7.4 or so after siting over night to "gas off." The second bowl we placed clean grow media and the top off water. Just after adding them, the pH was the same as the top off water, 7.4. The third bowl we placed grow stones from the system that had a bit of algae growing on them, we figured the algae might also play a roll in raising the pH. After adding the water, the ph was also 7.4. 

An hour after the initial start, we tested them again and the pH changed very little, not enough to even write about! So we decided to wait till morning to test again.

Here we saw some BIG results.  When we tested the next day the pHs have changed quite dramatically. The top off water had stayed the same (as we expected). The second bowl with the new grow stones has shot up to 8.4! The third bowl with the algae grow stones raised up to 8.6! So we are very sure that the stones play a roll in raising the pH.

The final pH testing. 

The next step, is how to address this problem. The grow stones used are made of 100% recycled glass. When purchased no thought was given to how it would effect the pH. After all, the equipment one uses to measure pH is made of glass! 

Serious thinking has been put into this problem. These are the options that we came up with.

     A. Switch out the grow stones

     B. Add pH balancer 

     C. Flush out the grow stones

     D. Do nothing and let the system "work itself out"

     

Replacing the grow stones and buying new media is very expensive and with so many established plants and bacteria, replacing it would set the system back. This will be the last resort.

Alex tried option B, and went through a whole bottle of "pH Down," a popular hydroponic pH corrector. This however had little effect. This means that there is something continually raising the pH. Another option will have to be used. 

Our local aquaponic / hydroponic shop, Route 66 Aquaponics, store owner Shaun helped us brainstorm. He suggested flushing the grow beds into a separate container to "rinse" the grow bed and add fresh, pH corrected water to replace taken out. We did a 35%- 45% water change and refilled it with pH neutral water. This helped the system a lot and cleared up the water but the pH is still high.

Our conclusion is to let the system try and "work itself out." The system is still quite young at only a few months old. Once it is fully established, which can take up to a year I have read, the system will be more stable. Plus the plants and fish look happy. The plants are flowering, the fish are mating, the systems inhabitants seem to not be affected by the high pH. 

Alex did say he had some tomato plants that were doing great during their vegetative stage, but as soon as they started flowering, they died off. This may have been due to the high pH.

Root 66 Aquaponics owner, Shawn explained to us that the tomatoes may not have had enough nutrients to flower since the system was even younger than. This makes sense. Plants need much more nutrients while flowering and at that time the system most likely did not have the beneficial bacteria build up to support a few flowering tomatoes plants.

Our Aquaponic dinner salad.
It has much more taste than salad bought in stores.

But as you can see the Blackwell System is Rockin' even with a high pH. We enjoyed a lovely salad and pasta tonight. We used salad and basil from the home system. Delicious.

Alex Blackwell harvesting his aquaponic garden. The salad was harvested just a few days ago too.
The plants, as you can see, are thriving despite the high pH.

*taken from Wikipedia

Blackwell System

Blackwell System

Today I introduce the Blackwell System. The owner Alex Blackwell, is a good buddy of mine. His system is awesome. It can be reproduced all over because it uses universal parts. It is in his basement so he needs supplemental lighting. He is using an eight bulb, T5 fluorescent light. It has two settings to choose between flowering and vegetative stages. The grow beds are two heavy duty plastic totes bought at Walmart. The whole system is nested in a stainless steal utility shelf. The bottom  portion is filled with a 75 gallon aquarium. The whole system has a 2' x 4' footprint, so it is very space efficient. 

Lights on! The plants are loving their aquaponic home.

The system is growing peppers, green and purple basil, mixed greens, and two types of melons! The melons were just planted so they are only sprouts at this point, but the rest is going amazingly! We have harvested the mixed greens three times in the past 16 days! And the next harvest is not far away. 

Peppers started flowering not too long ago.

Delicious mixed greens. It grows about as fast as we can eat it!
Everyone here loves here "fish poop salad!"

The nutrient machines that power this awesome system are just as beautiful as the greens they produce. I never knew tilapia were such colorful fish until I saw these! They have doubled their length and more than tripled their weight (all estimates at the moment) in  the two months or so Alex has had them. They are super lively and have personalities I did not expect.

Cool colors that I did not expect from tilapia.
Leave it to aquaponics to teach me even more!

This system is a perfect example for someone who wants to set up an aquaponics anywhere in their home or business. It has easy to find materials and simple mechanics. The Blackwell System has lots of cool odds and ends that work awesomely. I will highlight these in upcoming posts.

The Plant

The Plant

The other day I visited The Plant in Chicago. It was great to see! There was tons of innovative ideas and a very cool guided tour. The reason I went was to see the aquaponics but it turned out to be much more than that. The Plant serves as a small business incubator. I was knew to the term, but it allows new business to come in with lower start up costs. Each business is a cog in The Plants giant wheel. Everything going on in The Plant works in conjunction with each other. Spent brewer's grain gets used for mushroom substrate, CO2 from the Kombucha Tea process gets pumped into the aquaponic rooms to enrich the plants air. These are just two of the many symbiotic relationships the different business have with each other.

The Plant has plans to install an anaerobic digester. This technology will provide the building with Bio Gas. The Bio Gas will provide The Plant with all its electricity and be able to sell some back to the power company at night! It works like a mechanical stomach. The right blend of fatty, oily matter and solid, starchy matter (which The Plant is paid to remove) is combined, and constant slow rotation starts a fermentation process that creates Bio Gas. When the "stomach's" contents are done digesting there are two by-products. The liquid byproduct is sold to farmers as an organic nitrogen fertilizer. The solid byproduct is used as a compost. The property is just over two acres so most of the compost will also be sold.  

Although there is still a little ways to go with construction around the HUGE building, the aquaponics system in the basement is flourishing! The main food production bed and fish tanks can produce a 1/4 ton of veggies and 100 lbs of fish a month!

The main grow bed that produces a 1/4 ton of mixed
greens. Seed to harvest in 30-45ish days.

This is their LED grow bed. They are growing Curly Kale.
Only purple / blue LEDs are used to not waste valuable electricity
on light spectrums the plants do not use. Curly Kale is the
most nutrient leafy greens. Very efficient power to nutrition ratio.  

Producing 100 lbs of fish each month cannot be easy, but this system makes it look like people have been doing it for decades. They have the fish in raised IBC containers so the gravity pumps the water into the grow beds. 

One of many IBC containers used by The Plant. These are
easy to recycle for aquaponic needs. 

Settling tank and minimal mechanical filtration.
Behind, you can see the main grow bed. 

Aquaponic plumbing

                 

Myself, Felix Vogele, at The Plant

I was very impressed with The Plant's aquaponics systems. The whole process is about putting as little in as possible and getting as much as possible out. If all goes to plan, I can foresee many replica "plants" in the future.